Mobile communications networks are moving to the LTE standards defined by the Third Generation Partnership Project (3GPP). The LTE physical layer, which provides physical layer communications between user equipment (UE), such as mobile handsets, and evolved node Bs (eNode Bs) is defined in 3GPP TS 36.201 and TSs 36.211-216. The LTE physical layer provides modulation, physical channels, channel coding, and other aspects of physical layer communications between a UE and an eNode B
Before LTE equipment, such as eNode Bs, can be placed into service, the equipment must be tested under operational or simulated operational conditions. For example, in operation, an eNode B is required to handle simultaneous communications from multiple UEs. Accordingly, it is desirable for LTE test equipment to simulate multiple UE devices, including meeting all the timing requirements of the above-referenced LTE physical layer standards.
One particular timing requirement that must be met is the processing of a downlink radio frame in sufficient time for transmission of the corresponding uplink radio frame. In LTE networks, the downlink direction refers to transmission from the eNode B to the UE, and the uplink direction refers to transmission from the UE to the eNode B. The LTE physical layer defines a radio frame that is ten milliseconds in length and has ten subframes of one millisecond each. In the downlink direction, the physical downlink control channel (PDCCH) carries control information referred to as downlink control information or DCI. User data for plural UEs is carried on the physical downlink shared channel (PDSCH). The downlink DCI for subframe n is for the PDSCH data in the same subframe. The uplink DCI on subframe n has scheduling information for the physical uplink shared channel (PUSCH) in subframe n+4. This means that the UE or UE simulator has about four milliseconds from the time of reception of the scheduling information on the downlink signal to begin transmission of the corresponding uplink signal. In order to meet this constraint, the UE or multi-UE simulator needs to complete downlink processing, decode the downlink DCI, send grant information to a higher layer, get the protocol data unit (PDU) segmented from the radio link control (RLC) layer, perform all of the physical layer processing and modulation, and start transmission on the uplink. These and other timing requirements must be performed for each UE being simulated. Accordingly, there exists a need for a scalable architecture for LTE multi-UE simulation.